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Why are polysulfide rubbers used in seals and rocket propellants?

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Polysulfide rubbers, often known by the trade name Thiokol, are valued for their specific chemical properties that make them ideal for demanding industrial and aerospace applications.12

Why They Are Used in Seals

Polysulfide rubbers are highly effective for seals and gaskets due to their exceptional resistance to solvents, lubricants, and hydrocarbon oils. Because they contain a high sulfur content—approximately 80 percent by weight—they are resistant to swelling when exposed to these substances. Additionally, they are valued for their weather resistance and impermeability to gases, making them reliable for use in gasoline hoses and various mechanical sealing compositions.23

Why They Are Used in Rocket Propellants

In the aerospace industry, these elastomers serve as binders for solid rocket propellants. Their utility stems from their ability to be prepared as liquid polymers that can cure in place, as well as their status as high-density materials. While they possess poor tensile strength and abrasion resistance compared to other rubbers, their unique chemical structure allows them to function effectively as a matrix to hold propellant components together.213